JP2012211514A - System for supplying mixed fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology that keep a constant mixing ratio of a first fuel gas and a second fuel gas with a simple configuration even when the supply pressure of the fuel gas (the first and second fuel gases) varies.SOLUTION: A system for supplying mixed fuel includes: a first fuel gas supply path 1 for supplying the first fuel gas having a first calorific value to a mixing part M at a first supply pressure; a second fuel gas supply path 2 for supplying the second fuel gas having a calorific value that is lower than the first calorific value to the mixing part M at a second supply pressure that is higher than the first supply pressure; and a mixed gas path 3 for supplying a mixed gas of the first and second fuel gases that are mixed in the mixing part M. The second fuel gas supply path 2 includes a regulating means 5 for regulating the amount of the second fuel gas to be supplied to the mixing part M according to a change in gas pressure in the mixing part M when the amount of the first fuel gas to be supplied is changed, to regulate a calorific value of the mixed gas within a stable calorific value range.

Description

  The present invention provides a first fuel gas supply path for supplying a first fuel gas having a first calorific value to the mixing section at a first supply pressure, and a second fuel gas having a calorific value lower than the first calorific value, A second fuel gas supply path that supplies the mixing portion with a second supply pressure higher than the first supply pressure, and supplies a mixed gas of the first fuel gas and the second fuel gas mixed in the mixing portion. The present invention relates to a mixed fuel supply system including a mixed gas passage.

  Today, for example, manufacturing processes for producing biogas from food residues generated from food processing factories (beer factories, etc.) have been established, and the calorific value of biogas produced from such manufacturing processes varies. Very few and stable. The production volume is also increasing year by year.

In response to the above situation, for the purpose of realizing environmental facilities that are friendly to the earth, a so-called mixed fuel supply system that supplies so-called biogas generated on-site and mixes it with city gas, etc. where the amount of generated heat is controlled is proposed. Has been.
In such a mixed fuel supply system, a mixed gas of city gas as the first fuel gas and biogas as the second fuel gas having a lower calorific value than the first calorific value is used as the fuel gas. Typical examples of this type of mixed fuel supply system include a gas engine power generation system including a generator driven by a gas engine, a boiler system that generates steam by burning the mixed gas, and the like. In many boiler systems, the steam generation amount can be set stepwise.

An example of a gas engine power generation system in which such a mixed fuel supply system is employed is shown in Patent Document 1.
The system disclosed in Patent Document 1 is intended to stably operate a gas engine even if the amount of heat of the second fuel gas varies. In the technique disclosed in this document, when the amount of heat of the second fuel gas is reduced and the power generation output of the generator is lower than the target output, the first fuel gas supplied to the gas engine via the mixed gas path and the first fuel gas are output. The output control controller performs control to increase the opening of the throttle valve so as to secure the total heat quantity with the two fuel gases. Accordingly, the flow rate of the second air-fuel mixture sucked into the intake manifold increases, and the pressure in the intake manifold increases from the target pressure. At this time, the main fuel control controller increases the opening of the main fuel adjustment valve so that the pressure in the intake manifold returns to the target pressure.
As a result, the supply amount of the main fuel gas to the mixed gas passage increases, and the output controller returns the opening degree of the throttle valve. Thus, the shortage of the heat amount of the auxiliary fuel gas can be compensated by the heat amount of the main fuel gas, and the pressure in the intake manifold can be returned to the target pressure.

  In the technique described in Patent Document 1, in order to obtain a predetermined output on the mixed gas path side without considering a change in the mixing ratio between the first fuel gas and the second fuel gas, the supply flow rates of both fuel gases are adjust.

JP 2009-30492 A

  However, it may be preferable to adjust the output by supplying a mixed gas having a constant mixing ratio between the first fuel gas and the second fuel gas to the mixed gas passage and adjusting the opening of the throttle. This situation is, for example, a case where the gas engine wants to consume the second fuel gas in a system that is operated only with the first fuel gas whose calorific value is stably controlled, and the heat generation allowed for the gas engine. This is a case where the amount allowable width is limited to a predetermined width. When using such existing equipment, keep the mixing ratio of the first fuel gas and the second fuel gas constant, and maintain the calorific value of the mixed gas within a predetermined fluctuation range. Therefore, it is necessary to supply the gas engine with a mixed gas having a flow rate corresponding to the total calorific value in accordance with the output generated in the above.

  Therefore, when supplying such a first fuel gas and a second fuel gas to a gas engine, by maintaining the mixing ratio of the mixed gas, consumption of the second fuel gas while stabilizing the heat quantity of the mixed gas. It is possible to plan. As a configuration of such a mixed combustion system, as shown in FIG. 4 (configuration example for a gas engine power generation system) of the present specification, the pressure of the mixed gas is detected in the mixer, and the pressure is The supply flow rate F1 of the first fuel gas is controlled by the flow rate adjustment valve FCV-1 so as to be the target pressure, and the mixing ratio of the first fuel gas and the second fuel gas is previously set with respect to the supply flow rate F1. A configuration is conceivable in which the supply flow rate F2 of the second fuel gas is determined so that the predetermined supply flow rate ratio is set, and the second fuel gas is controlled by the flow rate adjustment valve FCV-2.

  However, in this configuration, in addition to a pair of flow rate detectors, flow rate adjustment valves and controllers being required, the supply flow rate of the second fuel gas is determined from the supply flow rate ratio of the second fuel gas to the first fuel gas. Since the ratio setting device to be determined is required, the equipment becomes complicated and the cost is increased.

  The object of the present invention is to provide a simple configuration for the mixing ratio of the first fuel gas and the second fuel gas even if the supply pressure of the fuel gas (first fuel gas and second fuel gas) fluctuates. An object of the present invention is to provide a mixed fuel supply system that can be maintained constant.

[Configuration 1]
In order to achieve the above object, the characteristic configuration of the mixed fuel supply system of the present invention is as follows:
A first fuel gas supply path for supplying a first fuel gas having a first calorific value to the mixing section at a first supply pressure;
A second fuel gas supply path for supplying a second fuel gas having a heat generation amount lower than the first heat generation amount to the mixing unit at a second supply pressure higher than the first supply pressure;
A mixed gas path for supplying a mixed gas of the first fuel gas and the second fuel gas mixed in the mixing unit,
In the second fuel gas supply path, the supply amount of the second fuel gas supplied to the mixing unit is adjusted according to a change in gas pressure in the mixing unit accompanying a change in the supply amount of the first fuel gas. And an adjustment means for adjusting the calorific value of the mixed gas to a predetermined stable calorific value range.

[Operation effect 1]
According to the above configuration, the mixing unit is supplied with the first fuel gas from the first fuel gas supply path, and is supplied with the second fuel gas from the second fuel gas supply path. Is done. The adjusted mixed gas is supplied from the mixed gas path to a portion where gas consumption is performed.

  Here, for example, the first fuel gas is assumed to be a city gas, natural gas, etc., which has a high calorific value and has a stable component and is used as the main fuel, and the second fuel gas has a low calorific value such as biogas, coal mine gas, etc. Assuming that, the system configuration in the case where it is desired to efficiently use the mixture by mixing the second fuel gas, which is limited in demand, with the general-purpose first fuel gas.

  In such a configuration, when the demand for the mixed gas changes, the supply amount of the first fuel gas changes according to the demand for the mixed gas, and with the change in the supply amount of the first fuel gas, The gas pressure in the mixing part changes. On the other hand, if the second fuel gas whose calorific value is lower than the first calorific value is to be supplied to the mixing section at a second supply pressure higher than the first supply pressure, the first fuel gas Even if the supply pressure of fluctuates, the second fuel gas can be reliably supplied to the mixing section.

  Then, when it is desired to supply the second fuel gas at a predetermined ratio with respect to the first fuel gas, the supply pressure of the second fuel gas with respect to the supply pressure of the first fuel gas needs to be maintained constant. When the gas pressure in the portion changes, the ratio of the supply pressure of the second fuel gas to the supply pressure of the first fuel gas changes accordingly. Therefore, when the second fuel gas supply path is provided with an adjusting means for adjusting the supply amount of the second fuel gas supplied to the mixing unit, the heat generation amount of the mixed gas is adjusted to the stable heat generation amount range. That is, the ratio between the supply amount of the first fuel gas and the supply amount of the second fuel gas can be maintained substantially constant, and stable consumption of the second fuel gas can be achieved.

[Configuration 2]
A valve inlet through which the second fuel gas flows, a valve outlet through which the second fuel gas flows out, and a second fuel gas inlet through which the second fuel gas upstream from the valve inlet is guided, In the valve box, the pressure adjustment chamber connected to the second fuel gas introduction port and the valve hole opening always connected to the valve inlet and communicating with the valve outlet can be adjusted according to the position of the valve body. A gas flow chamber connected to the valve through the diaphragm, and as the pressure on the valve outlet increases, the diaphragm is displaced so that the opening of the valve hole is reduced, and the valve body is moved. It is preferable that the adjusting means is constituted by a flow rate adjusting valve that moves the valve body so that the diaphragm is displaced and the opening degree of the valve hole is increased as the outlet side pressure decreases.

[Operation effect 2]
If the flow rate adjusting valve is provided as the adjusting means and the ratio between the supply amount of the first fuel gas and the supply amount of the second fuel gas can be maintained substantially constant, the second fuel can be configured with a very simple configuration. Stable consumption of gas can be achieved. As the flow rate adjusting valve, a pressure adjusting chamber that is connected to the second fuel gas inlet in the valve box, a valve that is always connected to the valve inlet, and communicates with the valve outlet according to the position of the valve body. It is possible to employ a configuration in which a gas circulation chamber connected to adjust the opening degree of the hole is provided via a diaphragm. With such a configuration, as the pressure on the valve outlet side increases, the diaphragm is displaced to move the valve body so as to reduce the opening of the valve hole, and as the pressure decreases on the outlet side, The reason why the diaphragm can be displaced to increase the opening of the valve hole can be explained as follows.

In the mixed gas path, the first and second fuel gases are consumed and a predetermined amount of the second fuel gas is circulated, and the pressure adjustment chamber pressure is P1, the gas circulation chamber pressure is P2, and the diaphragm is displaced. Then, assuming that the force that moves the valve body so as to increase the opening of the valve hole is S, in a state where these forces are balanced,
P1 = P2 + S (S> 0)
The relationship holds.

When the consumption amount of the first and second fuel gases is reduced from this state, the pressure in the mixing section increases, so as the supply amount decreases,
P2 → P2 + ΔP2 (ΔP2> 0)
P1 → P1 + ΔP1 (ΔP1> 0)
S → S + ΔS
In equilibrium,
(P1 + ΔP1) = (P2 + ΔP2 + S + ΔS)
The relationship is established. If this equation is transformed,
ΔS = ΔP1−ΔP2
The relationship holds.

Here, since the pressure fluctuation occurs on the P2 side, the flow rate adjusting valve works as a throttle,
ΔP2> ΔP1
The relationship holds.

Therefore,
ΔS = ΔP1−ΔP2 <0
Thus, in the equilibrium state after the decrease in the supply amount of the second fuel gas, the equilibrium is achieved at the diaphragm position where the opening of the valve hole becomes small.

  That is, as the consumption amounts of the first and second fuel gases decrease, the flow rate adjusting valve functions as an adjusting means for decreasing the supply amount of the second fuel gas. Further, since the degree of decrease in the supply amount of the second fuel gas at this time is determined by the relationship between ΔP2 and ΔP1, the higher the function as the throttle of the flow rate adjusting valve, the more the flow rate variation of the second fuel gas occurs. It will be. Conversely, as the consumption amounts of the first and second fuel gases increase, the flow rate adjusting valve functions as an adjusting means for increasing the supply amount of the second fuel gas. Therefore, the calorific value of the mixed gas can be adjusted to the stable calorific value range, that is, the ratio between the supply amount of the first fuel gas and the supply amount of the second fuel gas can be maintained substantially constant. In addition, stable consumption of the second fuel gas can be achieved.

  Note that, in such a configuration, the throttle function of the flow rate adjustment valve is to provide a separate throttle on the valve inlet side of the flow rate adjustment valve downstream of the connecting portion to the second fuel gas introduction port. For example, the relationship between ΔP2 and ΔP1 can be changed.

[Configuration 3]
In addition, the mixed gas path is provided with an engine that can be stably operated by receiving fuel gas in a predetermined stable heating value range, and the amount of fuel gas supplied to the engine is determined according to the state of exhaust gas discharged from the engine. Supply fuel gas amount control means for controlling may be provided.

[Operation effect 3]
When an engine is provided in the mixed gas path and the mixed fuel supply system is configured as a fuel gas supply source for driving the engine, the engine adjusts the amount of the supplied mixed fuel in accordance with fluctuations in its output. . Since the amount of the mixed fuel can be determined according to the state of the exhaust gas discharged from the engine, the state of the exhaust gas discharged from the engine can be monitored and controlled by the supply fuel gas amount control means.

  When the amount of mixed gas to be supplied to the engine is determined, the suction pressure at which the engine sucks the mixed gas from the mixed gas path is determined, and the amount of fuel gas supplied to the mixed gas is determined. At this time, the amounts of the first and second fuel gases are determined by the relationship between the gas supply pressure of the first fuel gas supply passage and the gas supply pressure of the second fuel gas supply passage, and the first fuel gas having the first calorific value. On the other hand, the supply amount of the second fuel gas whose calorific value is lower than that of the first calorific value is sucked into the second fuel gas passage that is supplied to the mixing portion at a second supply pressure higher than the first supply pressure. Determined based on pressure.

  When the suction pressure changes according to the engine output, P2 in the above relational expression changes, and when the engine output increases and the suction pressure increases (when P2 decreases), the supply of the second fuel gas When the engine output decreases and the suction pressure decreases (when P2 increases), the supply of the second fuel gas decreases, and the supply of the second fuel gas is performed in accordance with the change in the supply amount of the mixed gas. The amount will change.

  Then, the supply ratio of the second fuel gas with respect to the supply of the mixed gas is controlled so as not to change substantially, so that the heating value of the mixed gas can be adjusted to the stable heating value range. That is, the ratio between the supply amount of the first fuel gas and the supply amount of the second fuel gas can be maintained substantially constant, and the stable consumption of the second fuel gas can be achieved.

  Therefore, it is possible to provide a mixed fuel supply system capable of facilitating the effective use of low-calorie gas such as biogas and coal mine gas, which has been limited in conventional use forms, and can be used for driving engines and boilers. I can do it now.

It is a flowchart of the mixed fuel supply system of this invention. It is a vertical side view of a flow regulating valve. It is a figure which shows the relationship between an engine output (electric power generation output) and gas consumption. It is a flowchart of the conventional mixed fuel supply system.

  Below, the mixed fuel supply system of this invention is demonstrated. Preferred examples are described below, but these examples are described in order to more specifically illustrate the present invention, and various modifications can be made without departing from the spirit of the present invention. The present invention is not limited to the following description.

[Mixed fuel supply system]
As shown in FIG.
A first fuel gas supply path 1 for supplying a first fuel gas having a first heat generation amount from the first fuel gas supply unit 10 to the mixing unit M at a first supply pressure; and a heat generation amount higher than the first heat generation amount The second fuel gas supply path 2 for supplying a low second fuel gas from the second fuel gas supply unit 20 to the mixing unit M at a second supply pressure higher than the first supply pressure, and mixing in the mixing unit M A mixed gas passage 3 for supplying a mixed gas of the first fuel gas and the second fuel gas,
In the second fuel gas supply path 2, the supply amount of the second fuel gas supplied to the mixing unit M is changed according to a change in gas pressure in the mixing unit M accompanying a change in the supply amount of the first fuel gas. Adjusting means 5 for adjusting and adjusting the calorific value of the mixed gas to the stable calorific value range is provided.

  As a specific example, city gas is used as the first fuel gas, biogas obtained by methane fermentation of biomass is used as the second fuel gas, and 2 kPa is used as the first supply pressure. As the second supply pressure, about 3 kPa can be assumed.

  The mixed gas passage 3 is provided with an engine 6 that can be stably operated by receiving fuel gas in a predetermined stable calorific value range, and the amount of fuel gas supplied to the engine 6 is discharged from the engine 6. A supply fuel gas amount control means 7 for controlling the exhaust gas according to the state of the exhaust gas is provided.

  The supply fuel gas amount control means 7 is configured to freely open and close a flow rate adjustment valve 31 provided in the mixed gas passage 3 based on an output of an oxygen sensor 81 provided in the exhaust gas passage 8 of the engine 6. By opening and closing the valve 31, the fuel gas suction pressure from the mixing section M is adjusted, and the amount of mixed gas supplied to the engine 6 is adjusted. Specifically, the supplied fuel gas amount control means 7 receives the output from the oxygen sensor 81, and if the output is smaller than a predetermined value, adjusts the flow rate adjusting valve 31 in the opening direction, and the output is If it is larger than the predetermined value, the flow rate adjusting valve 31 is adjusted in the closing direction. Thereby, the ratio (A / F) of the air supply amount from the air supply passage 4 provided in the mixed gas passage 3 to the mixed gas amount is maintained at a predetermined amount, and the amount of mixed gas consumed is determined. When the fuel gas suction pressure in the mixing section M is determined, the mixing ratio of the first fuel gas and the second fuel gas is adjusted by the adjusting means 5, and the amount of heat of the mixed gas is set to a predetermined value suitable for the operation of the engine 6. Adjust to the stable calorific value range.

  In addition, between the first fuel gas supply unit 10 and the mixing unit M and between the second fuel gas supply unit 20 and the adjusting unit 5, the supplied gas is rectified and stably supplied. Control valves and the like are provided.

[Adjustment means]
As the adjusting means 5, a flow rate adjusting valve shown in FIG. 2 is used.

  The flow rate adjusting valve as the adjusting means 5 is always connected to the pressure adjusting chamber 50 </ b> A connected to the second fuel gas inlet 51 in the valve box 50 and to the valve inlet 52. A gas circulation chamber 50B is connected via a diaphragm 56 so that the opening degree of the valve hole 55 communicating with the valve outlet 53 can be adjusted according to the position. The valve outlet 53 is piped to the mixing part M side, and the valve inlet 52 is piped to the biogas supply source side as the second fuel gas supply part 20 to constitute the second fuel gas supply path 2. The valve inlet 52 of the second fuel gas supply path is provided with a throttle portion 57a that constitutes a flow meter 57, and branches from the second fuel gas supply path 2 upstream of the throttle portion 57a. A pilot passage 21 for introducing fuel gas is connected to the second fuel gas inlet 51 in the pressure adjusting chamber 50A.

  A spring 58 for restricting the displacement of the diaphragm 56 is provided between the diaphragm 56 and a peripheral portion of the valve hole 55, and a spring receiver 58a for receiving the spring 58 is provided, and a valve disposed in the gas circulation chamber 50B. The body 54 is fixed to the diaphragm 56 together with the spring receiver 58a. As a result, the diaphragm 56 is displaced with the pressure increase on the valve outlet 53 side to move the valve body 54 so as to reduce the opening of the valve hole 55, and with the pressure decrease at the valve outlet 53. Then, the valve body 54 is moved so that the diaphragm 56 is displaced and the opening of the valve hole 55 is increased.

[Engine operation example]
In the mixed fuel supply system having such a configuration, when the engine 6 is operated to drive the generator (not shown), the flow rate of the city gas (first fuel gas) is changed according to the fluctuation of the load output of the generator. As a result of examining how the flow rate of the biogas (second fuel gas) fluctuated, it was as shown in FIG.

  From FIG. 3, the total gas flow rate of the first and second fuel gases and the flow rate of the second fuel gas (biogas flow rate) are circulated so as to increase in proportion to the power generation output of the engine 6. The mixing ratio of the fuel gas and the second fuel gas is kept almost constant. In other words, it was found that the engine 6 is supplied with a mixed gas in a stable calorific value range as fuel and can be operated stably.

  The mixed fuel supply system of the present invention can be used, for example, in a system that generates power by supplying biogas as a fuel gas directly from a biogas generator to a gas engine. The engine can be used to operate an engine that can be stably operated by being supplied with fuel gas in a stable calorific value range.

1: 1st fuel gas supply path 10: 1st fuel gas supply part 2: 2nd fuel gas supply path 20: 2nd fuel gas supply part 21: Pilot flow path 3: Mixed gas path 31: Flow control valve 4: Air Supply path 5: Adjustment means 50: Valve box 50B: Gas distribution chamber 51: Second fuel gas introduction port 52: Valve inlet 53: Valve outlet 54: Valve body 55: Valve hole 56: Diaphragm 57: Flow meter 57a: Restriction part 58: Spring 6: Engine 7: Supply fuel gas amount control means 8: Exhaust gas path 81: Oxygen sensor M: Mixing section

Claims (3)

A first fuel gas supply path for supplying a first fuel gas having a first calorific value to the mixing section at a first supply pressure;
A second fuel gas supply path for supplying a second fuel gas having a heat generation amount lower than the first heat generation amount to the mixing unit at a second supply pressure higher than the first supply pressure;
A mixed gas path for supplying a mixed gas of the first fuel gas and the second fuel gas mixed in the mixing unit,
In the second fuel gas supply path, the supply amount of the second fuel gas supplied to the mixing unit is adjusted according to a change in gas pressure in the mixing unit accompanying a change in the supply amount of the first fuel gas. A mixed fuel supply system comprising adjusting means for adjusting the calorific value of the mixed gas to a predetermined stable calorific value range.   A valve box comprising a valve inlet through which the second fuel gas flows, a valve outlet through which the second fuel gas flows out, and a second fuel gas inlet through which the second fuel gas upstream from the valve inlet is guided. Inside, a pressure adjustment chamber that is connected to the second fuel gas inlet, and a valve hole that is always connected to the valve inlet and communicated with the valve outlet according to the position of the valve body. A gas flow chamber, which is provided via a diaphragm, and moves the valve body so that the diaphragm is displaced and the opening of the valve hole is reduced as the pressure at the valve outlet increases, and the valve outlet 2. The mixed fuel according to claim 1, wherein the adjusting means is configured by a flow rate adjusting valve that moves the valve body so that the diaphragm is displaced to increase the opening of the valve hole as the pressure decreases. Supply system.   The mixed gas path is provided with an engine that can be stably operated by receiving fuel gas in a predetermined stable calorific value range, and the amount of fuel gas supplied to the engine is controlled according to the state of exhaust gas discharged from the engine. The mixed fuel supply system according to claim 1, further comprising a supply fuel gas amount control means.

Images